(1) Field of the Invention
The present invention relates to the field of display devices. More specifically, the present invention relates to the field of flat panel display devices utilizing liquid crystal display (LCD) technology.
(2) Prior Art
Flat panel displays or liquid crystal displays (LCDs) are popular display devices for conveying information generated by a computer system. Many types of flat panel displays are typically back-lit or edge-lit. That is, a source of illumination is placed behind the LCD layers to facilitate visualization of the resultant image. Flat panel LCD units are used today in many applications including the computer component and computer peripheral industries where flat panel LCD units are an excellent display choice for lap-top computers and other portable electronic devices.
In the field of flat panel LCD unit devices, much like conventional cathode ray tube (CRT) displays, a white pixel is composed of a red, a green and a blue color point or xe2x80x9cspot.xe2x80x9d When each color point of the pixel is illuminated simultaneously and with the appropriate intensity, white can be perceived by the viewer at the pixel""s screen position. To produce different colors at the pixel, the intensities (e.g., brightness) to which the red, green and blue points are driven are altered in well known fashions. The separate red, green and blue data that correspond to the color intensities of a particular pixel are called the pixel""s color data. Color data is often called gray scale data. The degree to which different colors can be achieved by a pixel is referred to as gray scale resolution. Gray scale resolution is directly related to the amount of different intensities to which each red, green and blue point can be driven.
The aspect ratio of a monitor refers to the number of pixels the monitor provides along the horizontal direction with respect to the number of pixels the monitor provides along the vertical direction. Assuming that the pixels are square, e.g., the pitch between each RGB triad is the same in both horizontal and vertical directions, the aspect ratio can also refer to the horizontal length with respect to the vertical height. Monitors not having a wide aspect ratio include the VGA standard, the SVGA standard, the XGA standard, SXGA standard and the UXGA standard. For instance, the VGA standard has 640 pixels by 480 pixels having a 1.3 to 1 aspect ratio (xe2x80x9c1.3:1xe2x80x9d). The SVGA standard has 800 pixels by 600 pixels having an aspect ratio of 1.3:1. The XGA standard has 1024 pixels by 768 pixels having an aspect ratio of 1.3:1. The SXGA standard has 1280 pixels by 1024 pixels having an aspect ratio of 1.25 to 1 (xe2x80x9c1.25:1xe2x80x9d). And, the UXGA standard has 1600 pixels by 1200 pixels having an aspect ratio of 1.3:1. The VGA standard, the SVGA standard, the XGA standard, SXGA standard and the UXGA standard have been commonly implemented in CRT display technology and also in some flat panel display technologies.
The areas of photography and publishing require the manipulation of high information content images and text. These areas are limited in the amount of information that can be displayed at one time by the size and aspect ratio of their display devices, typically CRT displays. It would be preferable, within these industries, to be able to display multiple photos, pages of text, or images side by side for either absorbing information at a higher rate or comparing them with each other, e.g., by using a wide aspect ratio display.
Wide aspect ratio displays include the high definition television standard, or HDTV standard, having 1920 pixels by 1080 pixels with an aspect ratio of 1.9 to 1 (xe2x80x9c1.9:1xe2x80x9d). Also, the UXGA-Wide standard is a wide aspect ratio display and has 1920 pixels by 1200 pixels with aspect ratio of 1.6 to 1 (xe2x80x9c1.6:1xe2x80x9d). The SXGA-Wide standard is a wide aspect ratio display and has 1600xc3x971024 pixels with an aspect ratio of 1.6:1. And the XGA-Wide standard is a wide-aspect ratio display and has 1280 pixels by 768 pixels having a 1.7 to 1 aspect ratio (xe2x80x9c1.7:1xe2x80x9d). However, CRT monitors have difficulty in displaying information in a wide aspect ratio format for several reasons. First, because the bulb of a CRT encloses a large volume of high vacuum, it is structurally unsound for the bulb to deviate from a shape roughly square in cross section.
Second, as shown in FIG. 1, CRT display technology has some trouble individually addressing the edge located pixels 14a and 14c in a wide aspect display format. FIG. 1 illustrates a top view of a cathode ray tube 10 that can be used for a wide aspect ratio CRT display including an electron gun 12 with beam directing magnets 5. Because each phosphor dot in a CRT 10 is addressed by a beam from one of three electron guns 12 being fired from a common point located behind but centered over the active area 14, addressing a dot at the extreme edge 14a of the screen or at the corners is very difficult. This is because of the oblique angle that the beam 12 must make with the area surface of the phosphor screen 14 and its shadow mask which can cause scanning errors. These errors result in nonuniform color and/or brightness of the displayed image.
Specifically, as the aspect ratio of the CRT increases, the angle at 18 becomes larger. As angle 18 becomes larger, the pixels 14a, which are located along the edge of the screen within phosphor layer 14, become more difficult for the beam 12a of the electron gun 12 to individually resolve. As a result, pixel cross-over or xe2x80x9cbleedingxe2x80x9d may occur for the pixels located at the edges of the screen. This bleeding does not occur with the pixels 14b which are located in the screen center because beam 12b can individually resolve pixels 14b. The result can be a non-uniform image which is very disadvantageous. One way to resolve this problem within CRT displays is to place the electron gun 12 back farther away from phosphor layer 14 thereby decreasing the maximum angle 18 for edge-located pixels 14a and 14c. However, this solution unfortunately leads to heavier, larger, bulkier glass leading to larger and more expensive CRT displays. The larger the vacuum tube 15 becomes, the harder it is to maintain the vacuum seal.
Another way to solve the above problem of individually addressing edge-located pixels is to slightly curve the display screen as shown in FIG. 1 to assist electron gun 12 in resolving the edge located pixels 14a and 14c. However, commercially a flat screen is the first choice for viewing images, not a curved screen, which tends to distort images and text displayed thereon. A third manner in which to solve the above problem is to alter the pixel density of the pixels located along the edge (e.g., pixels 14a and 14c) with respect to the pixel density of the center located pixels 14b. In other words, this solution increases the pixel pitch (e.g., distance from pixel center to pixel center) for pixels 14a and for pixels 14c compared to the center pixels 14b. For instance, pixel pitch for center pixels 14b is 0.25 mm and pixel pitch for corner pixels 14a is 0.28 mm in some prior art CRT displays. By increasing the pixel pitch for the edge located pixels 14a and 14c, the electron gun 1.2 can better resolve individual edge located pixels 14a and 14c. However, this solution adds the unfortunate side-effect of producing a non-uniform image with noticeable non-uniformities (e.g., non-linearity) located along the screen periphery.
In either of the solutions described above, wide aspect ratios CRTs are large and bulky. It would be advantageous to provide a wide aspect CRT that avoids the above problems. Liquid crystal flat panel displays have been used in the past. For example, U.S. Pat. Nos. 5,696,529 and 5,593,221 describe a flat panel display. However, LCD flat panel displays as needed in desktop publishing and other high quality image applications have heretofore not been manufactured with a wide aspect ratio.
Accordingly, the present invention offers a wide aspect ratio display monitor that is not bulky or heavy and can be readily handled. Further, the present invention offers a wide aspect ratio display monitor that displays a uniform image having uniform pixel pitch throughout the display screen. The present invention offers a wide aspect ratio display monitor that has high resolution and is capable of displaying high information content for text, graphics and other multi-media applications requiring high image quality. These and other advantages of the present invention not specifically described above will become clear within discussions of the present invention herein.
A wide aspect ratio flat panel display is described herein having high resolution for high information content display. The high resolution flat panel display with wide aspect ratio, of the present invention, readily solves the above problems associated with CRT displays. The flat panel display of the present invention is digitally addressed in an (x, y) matrix of pixels over the entire area of the display rather than from a single point. Therefore, addressing the extreme right/left edges or the corners of the display is not more difficult than addressing the pixels at the center of the screen. Also, since the pixels of the display are positioned in a definite, permanent location and not dependent upon the stability, intensity and accuracy of a traveling Gaussian beam, the image of the present invention is inherently more stable. Flat panel displays are also brighter because their light source is independent from its pixel addressing source. Since the body color of CRT phosphors is inherently white, liquid crystal flat panel displays can achieve a much higher contrast ratio which makes the information on the screen easier to discern. This results in much less eye fatigue for a desktop publishing user who often stares for hours at the display screen. Additionally, the present invention couples the above advantageous with white balance mechanisms that do not alter the dynamic grayscale range of the RGB colors. Therefore, the flat panel display of the present invention is ideally suited to high information content displays, e.g., for desktop publishing, tactical displays, photography, etc.
The present invention includes a large display area a liquid crystal flat panel display monitor having an aspect ratio that is greater than 1.3:1. In one embodiment, the aspect ratio is substantially 1.6:1, having 1,600 pixels across the horizontal and 1,024 pixels across the vertical. In this embodiment, the present invention is an SXGA-wide flat panel display monitor having high resolution for high information content display. The monitor of the present invention is particularly well suited for the display of text, graphics and other types of still and/or motion audio/visual works. The wide aspect ratio allows the display of multiple pages, side-by-side, thereby facilitating certain tasks such as desktop publishing, presentation of interactive windows, presentation of menus, chart viewing, digital photography, tactical military displays and weather and aircraft monitoring. The novel wide aspect ratio monitor also provides compensation film layers, rather than dual domain technology, for providing off axis viewing capability in the horizontal and vertical axis. The novel wide aspect ratio monitor also provides color balance adjustment. The color balancing mechanisms include the provision of two or more light sources, of differing color temperature, whose brightness is varied (and distributed through a light distribution mechanism) to adjust color temperature without altering the grayscale dynamic range of the RGB colors.
Multiple light source systems are described herein for color balancing within a liquid crystal flat panel display unit. The present invention also includes a method and system for altering the brightness of two or more light sources, having differing color temperatures, thereby providing color balancing of a liquid crystal display (LCD) unit within a given color temperature range. The embodiments operate for both edge and backlighting systems. In one embodiment, two planar light pipes are positioned, a first over a second, with an air gap between. The light pipes distribute light uniformly and independently of each other. The first light pipe is optically coupled along one edge to receive light from a first light source having an overall color temperature above the predetermined range (e.g., the xe2x80x9cbluexe2x80x9d light) and the second light pipe is optically coupled along one edge to receive light from a second light source having an overall color temperature below the predetermined range (e.g., the xe2x80x9credxe2x80x9d light). The color temperatures of the first and second light sources are selected such that the overall color temperature of the LCD can vary within the predetermined range by altering the driving voltages of the first and second light sources. In effect, the LCD color temperature is altered, without altering the grayscale dynamic range of the screen colors, by selectively dimming the brightness of one or the other of the light sources so that the overall contribution matches the desired LCD color temperature.
Specifically, one embodiment of the present invention includes a monitor comprising: a) a large area wide aspect ratio liquid crystal flat panel display screen, the large area wide aspect ratio liquid crystal flat panel display screen having high resolution for displaying high information content, the large area liquid crystal flat panel display screen comprising optical compensation film layers for providing increased off axis angle viewing capability in the horizontal and vertical directions; and b) electronic circuitry for receiving signals from a digital computer system and for driving the wide aspect ratio liquid crystal flat panel display screen. Embodiments include the above and wherein the wide aspect ratio liquid crystal flat panel display screen has an aspect ratio of 1.6:1. Embodiments include the above and wherein the high information content includes text information and graphics image information. Embodiments include the above and wherein the large area wide aspect liquid crystal flat panel display screen comprises an in-plane switching liquid crystal layer for improved viewing angle. Embodiments also include a display screen having an antiferroelectric layer.
Embodiments include the above and wherein the large area wide aspect ratio liquid crystal flat panel display screen is non-emissive and further comprises: a first light source of a first color temperature; and a second light source of a second color temperature different from the first color temperature, the first and second light sources positioned to illuminate the wide aspect ratio liquid crystal flat panel display screen with light having a net color temperature that is dependent on an intensity of the first light source and an intensity of the second light source wherein the first and the second light sources alter the net color temperature of the light, within a predetermined color temperature range, by controlling the intensity of the first light source and the intensity of the second light source.